The critical move looks to me like 19...Bd4, aiming to play ...e5 and block the e-file, or ...Bc5 to block the a3-f8 diagonal:

20 Bh5, threatening to take on e6 once again, 20...Nc5 21 Rd1 e5 22 Rxd4 (22 Qf6 draws immediately after 22...0-0 23 Qg5+) 22...exd4 23 Qf6 but again it's only a draw after 23...0-0 24 Qg5+.20...Kd8 is possible, 21 Bxf7 Qc6 22 Rd1, but now Black has to find the saving move 22...Qf3! as 23 Rxd4 Qxf7 24 Qh4+ Ke8 25 Qe4 is again 0-00 according to my computer, although White is a rook down!So, maybe 18 Qh6 is also drawn, without many (or any?) real winning chances for White?!